It is common practice to apply chemicals to a growing crop, for instance to help control pests, fungi or weeds.
Ground-based crop-spraying equipment commonly comprises a vehicle, e.g. tractor, carried body having an elongate framework or boom which extends laterally from the body and which supports nozzles which apply a spray mist of chemical/water mixture to the crop and its surroundings. Such a boom is often used to cover a working width of between 12 and 30 meters to minimise the number of passes required to cover a given area of land.
Spray booms are conventionally made from a space-frame of members, e.g. tubes, comprising laterally and vertically spaced longitudinally extending members joined at intervals by transverse cross-members, with the spray nozzles disposed within the boom framework for protection. It is not possible with such conventional spray booms to place the spray nozzles in any desired location along the boom since the cross members occupy positions at which it may be wished to place the spray nozzles.
Conventionally, the opposed arms of the spray boom each comprise at least two sections which are folded over against themselves and are then positioned against the sides of sprayer, e.g. tractor, for road transport/storage. Thus, where the hinge axes are vertical, the lateral width of the sprayer may be increased by several times the width of the spray boom during such road transportation and storage. It is important in some circumstances, e.g. when the sprayer is already wide, that the folded arms of the boom do not unduly increase lateral width of sprayer. Another way of folding the boom for storage and transportation involves hinging the boom sections about horizontal axes, but while this mitigates the problem of the folded width of the spray boom, it introduces instead the problem that during such folding of the arms of the boom, there is a risk of contact with overhead obstructions, e.g. power lines, due to movement of the arms through vertical arcs and due to the considerable length of the boom and its respective arm sections.
It is an object of the invention to mitigate these problems.